1. Field of the Invention
The present invention relates to the detection of exposure to HIV (Human Immunodeficiency Virus), the etioliogical agent of Acquired Immunodeficiency Syndrome (AIDS). In particular, a mouse monoclonal antibody, H37c94, and its epitope within HIV-2 gp41 are provided which form the basis of an immunoassay used to differentiate those individuals exposed to the HIV-2 virus from those exposed to the HIV-1 virus.
2. Description of Related Art
The nucleotide sequence of the proviral genome has been determined for several HIV isolates, including HIV-1 strains HTLV-III (Ratner et al., Nature (1985) 313:277); ARV-2 (Sanchez-Pescador et al., Science (1985) 227:484); LAV (Wain-Hobson et al., Cell (1985) 40:9); and CDC-451 (Desai et al., Proc. Natl. Acad. Sci. USA (1986) 83:8380). The nucleotide sequence of the HIV-2 ROD isolate was reported by Guyader et al. (Nature (1987) 326:662). The HIV-2 NIHZ isolate was reported by Zagury et al. (PNAS (1988) 85:5941-5945). Additional HIV sequences are found in Meyers et al., Human Retroviruses and AIDS 1988, A Compilation and Analysis of Nucleic Acid and Amino Sequences (Los Alamos National Laboratory, Los Alamos, N. Mex.).
One of the key serological targets for detection of HIV-1 infection is the transmembrane protein (TMP), gp41. Antibodies to this protein are among the first to appear at seroconversion, and the immune response to gp41 apparently remains relatively strong throughout the course of the disease as evidenced by the near universal presence of anti-gp41 antibodies in asymptomatic as well as all other clinical stages of AIDS. The bulk of the antibody response to the protein is directed toward a well characterized immunodominant region (Chang et al., Bio/Technology (1985) 3:905-909), broadly defined between amino acids 578 thru 613 (numbering by Meyers et al., for the HXB2 isolate). Specific, small sequences within the immunodominant region have been identified as forming the key immunogenic sequences, including RILAVERYLKDQQLLGIWGCS in which arg-1, ile-2, and lys-10 each play important roles in maintaining antigenicity of the peptide (Wang et al., Proc. Natl. Acad. Sci. U.S.A. (1986) 83:6159-6163), LGLWGCSGKLIC in which both cys residues appear to play key roles in maintaining antigenicity of the peptide (Gnann et al., J. Virology (1987) 61:2639-2641), and SGKLICTTAVPWNAS which may comprise an epitope hidden in the native virus but which is exposed and immunogenic during the course of the disease (Narvanen et al., AIDS (1988) 2:119-123). A human monoclonal antibody was raised which maps to the sequence GIWGCSGKLIC providing additional support for the central role this sequence may play as an immunogen (Banapour et al., J. Immunol. (1987) 139:4027-4033).
Other regions of gp41 apparently play only minor roles, if at all, in eliciting an immune response (Gnann et al., J. Infect. Diseases (1987) 156:261-267; and Windheuser and Wood, Gene (1988) 64:107-119), and have not been identified as being diagnostically useful.
Much less is known concerning the immunodominant epitope(s) of HIV-2 transmembrane protein, referred to as HIV-2 gp41 in this application, and research has been directed primarily toward using the immunodominant region of the protein as a serological target for differentiating exposure to HIV-2 from HIV-1. Gnaan et al. (Science (1987) 237:1346-1349) used a portion of the HIV-2 ROD immunodominant region in a synthetic peptide NSWGCAFRQVC, to detect antibody to HIV-2 and differentiate it from antibody to HIV-1. In addition, Cot et al. (AIDS Research and Human Retroviruses (1988) 4:239-241) also used immunodominant region peptides to differentiate human antibodies to HIV-2 gp41 from HIV-1 gp41. The HIV-2 peptide used was the sequence RVTAIEKYLQDQARLNSWGCAFRQVC. In both studies, the region utilized ended at the second cysteine residue. In neither case, nor in any other report, has the HIV-2 sequence HTTVPW been shown to have any diagnostic value as a serological target or an antigen for a monoclonal antibody.